Cardiorespiratory fitness and metabolic syndrome

Moderate physical activity has enormous public health implications on metabolic syndrome, CVD and type 2 diabetes.

Issue: October 2008

ByTrudy Gaillard, PhD, RN, CDE

Metabolic syndrome is defined as a conglomeration of risk factors known to be associated with increased risk of both atherosclerosis, cardiovascular disease and type 2 diabetes.

The National Cholesterol Education Adult Treatment Panel (ATP) III criteria for diagnosis of metabolic syndrome include three or more of the five components in adults. These are fasting glucose > 100 mg/dL, hyertriglyceridemia >150 mg/dL, low HDL-C <50 mg/dL for women and < 40 mg/dL for men, BP > 130/85 mmHg, and waist circumference > 35 for females and 40 for men. Ford et al used prevalence data from NHANES and reported that approximately 64 million Americans have metabolic syndrome. Initially, the purpose of defining the syndrome was to develop clinical criteria to identify individuals at risk for developing CVD and type 2 diabetes with the hope of developing primary prevention strategies.

Risk factors

Trudy Gaillard

Excessive weight (obesity) and lack of physical activity are two of the major factors associated with increasing metabolic syndrome risks. These two factors are increasing in both U.S. adults and children. Understanding how weight gain and lack of physical activity are associated with increased metabolic syndrome and CVD mobility and mortality are major public problems. Most studies have shown that increases in physical activity are associated with lower rates of metabolic syndrome and other CVD comorbid conditions.

Most importantly, there is an inverse relationship between metabolic syndrome and sedentary lifestyle. In fact, Ford et al studied the association between self-reported physical activity and prevalence of metabolic syndrome in the NHANES data. They demonstrated that adults who engaged in > 4 hours of sedentary behavior had higher prevalence of metabolic syndrome, whereas those who engaged in more self-reported activity had less metabolic syndrome. These studies, clearly demonstrated enormous CVD benefits of increased physical activity in lowering incidence of metabolic syndrome.

The relationships between physical activity and metabolic syndrome incidence and prevalence have been inconsistent in the literature. This may be due to the self-report nature of physical activity, especially in women in most previous studies. This issue is particularly important in black women who report less leisure time physical activity compared to white women. Cardiorespiratory fitness is best measured by maximal exercise stress test or VO2max test. This form of testing is a more reliable measure of physical activity and is less prone to underreporting than self-report.

LaMonte et al demonstrated that low levels of cardiorespiratory fitness were a strong and independent risk factor for metabolic syndrome. They compared subjects in the lowest third for cardiorespiratory fitness and found that the risk of developing metabolic syndrome was 20% to 26% lower among participants in the middle third and 53% to 63% lower among those in the highest third. Their study clearly demonstrated the protective effects of cardiorespiratory fitness on development of metabolic syndrome. In another study, Blair et al found low levels of cardiorespiratory fitness to be associated with higher all-cause mortality in men and women.

Finally, the interaction between VO2max and metabolic risk factors for CVD in women has been less studied, especially in black women. Black women at every age strata reported less leisure time physical activity when compared to white women and Hispanic women. Ironically, despite the lower level of reported physical activity and greater insulin resistance, black women have lower incidence of metabolic syndrome when compared to white women. This has been partly attributed to the higher serum HDL and lower triglycerides in black women than white women. Therefore, there is a disconnect in the relationship between metabolic syndrome and self-report leisure time physical activity in black women and other high risk ethnic populations.

Recently, a study conducted by Gaillard et al using quantitative VO2max showed higher rates of metabolic syndrome components in black women empirically categorized according to levels of VO2max (very low aerobic fitness < 21 mL/kg/min, low aerobic fitness 21.1 to 24.4 mL/kg/min and moderate aerobic fitness > 24.4 mL/kg/min, respectively). In this unpublished study, the overall prevalence of metabolic syndrome was 25% for the group, 41% for very low aerobic fitness, 25% for low aerobic fitness and 10.5% for moderate aerobic fitness group. Therefore, there is a need to examine the benefits of quantitative cardiorespiratory fitness and VO2max on the metabolic components of metabolic syndrome in black women.

In summary, higher levels of cardiorespiratory fitness and physical activity are associated with lower rates of metabolic syndrome as well as decreases in CVD and coronary heart disease. Therefore, there is a need for health care professionals to encourage moderate physical activity to all person regardless of obesity. We conclude, thus physical activity (albeit modest) has enormous public health implications on metabolic syndrome, CVD and type 2 diabetes in the general population.

Trudy Gaillard, PhD, RN, CDE, is an Assistant Professor of Medicine-Research in the Division of Endocrinology, Diabetes and Metabolism and the Diabetes Research Center at the Ohio State University Medical Center.

For more information:

Blair S, Kohl H, Paffenbarger R, et al. Physical fitness and all-cause mortality: A prospective study of healthy men and women. JAMA. 1989;262:2395-2401.

Crespo C, Keyeyian S, Heath G, Sempos C. Leisure-time physical activity among U.S. adults. Results from the Third National Health and Nutrition Examination Survey. Arch Intern Med.

Expert panel on detection, evaluation and treatment of high blood cholesterol in adults: Executive summary of the third report of the National Cholesterol Education Program (NCEP) Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults (Adult Treatment Panel III). JAMA. 2001;285:2486-2497.

Farrell S, Cheng Y, Blair B. Prevalence of metabolic syndrome across cardiorespiratory fitness levels in women. Obes Res. 2004;12:824-830.

Ford E, Giles W, Dietz W. Prevalence of the metabolic syndrome among U.S. adults: Findings from the Third National Health and Nutrition Examination Survey. JAMA. 2002;287:356-359.

Ford E, Kohl H, Mokdad A, Ajani U. Sedentary behavior, physical activity, and the metabolic syndrome among U.S. adults. Obes Res. 2005;13:608-614.

Gaillard T, Sherman W, Devor S, et al. Importance of aerobic fitness in cardiovascular risk in sedentary overweight and obese African American women. Nurs Res. 2007;56:407-415.

Laaksonen D, Lakka H, Salomen J, et al. Low levels of leisure-time physical activity and cardiorespiratory fitness predict development of the metabolic syndrome. Diabetes Care. 2002;25:1612-1618.

LaMonte M, Barlow C, Jurca R, et al. Cardiorespiratory fitness is inversely associated with the incidence of metabolic syndrome: A prospective study of men and women. Circulation. 2005;112:505-512.